Breaking the Rule of Three

Here’s a piece of often-repeated advice for planting perennials: Always plant in odd numbers, in groups of at least three.

This is good advice. An odd number of plants can be arranged in an irregular cluster, which looks more natural than a straight line or block shape. Using at least three ensures this group will have some substance; it will be noticed.

But there are times when you can’t follow this rule. Perhaps you’re working in a space that won’t fit three of the desired plant. Perhaps you’re sticking to a tight budget and buying one more plant would put you over.

Nan Ondra and Stephanie Cohen share good advice for such a quandary in their book The Perennial Gardener’s Design Primer. In such situations, they say, just keep in mind the habit of the perennial in question. Unless it has a strong, distinct form, such as an agave, there’s a good chance that in a few years you won’t be able to tell just how many plants you originally placed in the grouping—they will pretty much blend into one mass.

As for “planting in ones”—this too can work. Just don’t be self-conscious about it. Make that single plant into a true specimen by giving it a noticeable position, such as next to a gate or door, in the very center of the border or at the end of a path. Be forward about the placement and it won’t look out of place, random or lost.

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2 thoughts on “Breaking the Rule of Three”

When I find I’m going to just buy one, such as a coral Bell, or hosta, especially if it’s small, I plant those in front of a larger rock so the accent is on the one plant. The rock shows off the plant and I’m just real satisfied with what I’ve created. Have lots of positive feed back about it as well.
Thanks you for all your great ideas.

That sounds like a great strategy, Marlene. The rock would act as both an anchor tying the plant to the garden, and a backdrop. Thanks for taking the time to share this with everybody and it is something I’ll try in my own garden. Whenever I dig a hole I harvest at least one good-size rock!